The present invention relates to a method for removing excrement, made up of feces and urine, of animals kept in a stall, in particular pigs. In addition, the invention relates to an apparatus for executing the method.
In wide use in practice, and therefore generally known, are stalls whose floor surface is constructed so as to be entirely or partially permeable to excrement, for example as a slatted floor, a liquid manure channel for the collection and common drainage of feces and urine being provided under the permeable floor. The liquid manure channel has a relatively large capacity, because it is used not only to collect but also to store feces and urine, i.e., liquid manure. From time to time the liquid manure channel is emptied, whereby the liquid manure is then pumped either into a liquid manure container outside the stall or into a transport vehicle so that it can be applied on a field surface. Significant environmental pollution, due to the formation and diffusion of ammonia and methane gas, disadvantageously arises both in the stall during the collection and storing of the liquid manure and also in the surroundings of the liquid manure container, or in the surroundings of a field surface dunged with liquid manure. In particular, unpleasant odors arise that are felt by most of those affected to be strongly disturbing, and that also have an adverse effect on the health of the animals kept in the stall. In order to avoid damage to the animals kept in the stall, an intensive exchange of air is required, which takes place using ventilators, for which a considerable amount of electrical energy must be used. However, this intensive air exchange again results in an increased discharge of harmful gas outside the stall.
A partial reduction of the disadvantages stated above, in particular in the interior of the stall, can be achieved by mechanical cleaning apparatuses, such as those known for example from DE 43 12 128 A1 or from DE 21 27 370 A1. Using these known cleaning apparatuses, feces and urine are transported together from a deposition surface into a liquid manure collection region, so that a reduced degree of pollution is achieved inside the stall. However, here as well the environmental pollution outside the stall, due to liquid manure stored in a container and due to liquid manure applied on field surfaces as dung, occurs to an unreduced extent.
From DD-PS 21 15 96, a method is known for the fractional mechanical drainage of liquid manure in animal stalls, in particular for calf stalls. This method is characterized in that the following are preferably combined: a perforated floor extending over as much of the overall space occupied by the animals as possible, a large portion of said floor being occupied by holes, and a fecal surface, inclined transverse to the row of standing animals and having a conduit for urine and having a blade that is divided into sections and that has a slow advance rate, as well as having separate dumping pits for the solid and the liquid phase at the end of the row of standing animals, with connection to separate supply containers. Beyond the separate carrying off and storage of feces and urine, however, this prior art does not supply any indication as to whether and in what way a further treatment of feces and/or urine is to take place.
The object of the present invention is therefore to create a method and an apparatus for the execution of the method of the type named above that avoid the stated disadvantages and with which an improvedxe2x80x94in particular, more environmentally friendly and less harmful to animalsxe2x80x94disposal of the excrement is achieved.
With respect to the method, the object is achieved by a method of the type named above that is characterized in that the carrying off of feces and urine from the stall and the storing and/or further treatment thereof takes place in a fresh state, before the beginning of a decomposition, and in that the further treatment of the feces comprises at least the following steps:
a surface enlargement of the fresh feces, and
a drying of the feces to a moisture content that prevents a decomposition.
It is essential to the invention that feces and urine are carried off from the stall not only separately from one another but also in a still-fresh state, before the beginning of a decomposition, so that in the stall no stress due to excrement stored there and deposited there for a longer period, and the decomposition products thereof, can occur. In addition, it is provided according to the invention that the further treatment of the feces comprises at least the two described steps. The further treatment serves first of all to prevent the feces from developing environmentally harmful properties as a result of decomposition, and in addition to make the feces profitably recoverable. Since, due to the separation from the urine, the fresh feces conveyed out of the stall already has a relatively low moisture content, and because according to the invention a surface enlargement of the feces is carried out, for example using a vibrating apparatus or a perforated plate, with the inventive method it is possible for the first time to dry the feces with a reasonable energy expense. The drying temperature can thereby be relatively low, so that it is possible to use waste heat for the drying; moreover, the drying temperature should remain below 60xc2x0 C., in order to avoid an undesirable decomposition caused by temperature. In its dried state, the feces can be stored and transported, because, due to the lack of liquid in the feces, no bacterial decomposition can take place, and because it is then also hardly possible any longer for unpleasant odors to arise.
After being removed from the stall, the urine does not absolutely have to be further treated, because between 85 and 99% of all nutrients and salts remain in the solid material, i.e., in the feces. For this reason, the urine can and may be applied directly onto farming surfaces, or may be drained off as sewage.
With the inventive method, a drastic reduction of the ammonia content in the stall air is achieved, so that the ventilation inside the stall can be correspondingly reduced. Moreover, the harmful formation of methane gas in the stall is precluded. The number of germs in the stall air is drastically reduced, because, due to the separate carrying off of feces and urine in a fresh state, no bacterial decomposition can occur inside the stall. In contrast to liquid manure, the carried-off urine does not decompose, because the bacteria still contained in the urine are not presented with a sufficient quantity of nutrients. For this reason, a conversion of the urea contained in the urine into ammonia can no longer occur.
The further treatment of the feces and, if necessary, of the urine can take place with a delay, including intermediate storage, or can take place immediately. The choice here is made in particular according to the quantities of urine and feces that occur and are to be treated, and also according to whether the respective apparatus for further treatment is better operated continuously or in charge-by-charge fashion.
A preferred development of the method provides that the drying of the feces takes place at first only until a moisture content between approximately 10 and 25 weight % has been reached, and that the feces is then pressed, with further reduction of moisture, to form pressed pieces having a residual moisture content that prevents a decomposition. The pressing of the feces to form pressed pieces necessarily results in a reduction in moisture, because the pressure exerted presses out a large part of the previously contained moisture, without its being necessary to provide a separate drying step for this purpose. The previous drying can therefore be limited to the indicated incomplete drying, which limits the expense for the previous drying, in particular the energy expense. Moreover, in comparison with dried feces in powdered form, the feces pressed to form pressed pieces is easy to handle and can be stored and transported easily, which significantly improves and simplifies the further use of the dried feces.
A preferred method for the separation of feces and urine, which advantageously requires a low expense and the same time ensures a high degree of separation is provided wherein the separation of feces and urine takes place in that the urine is conducted from an excrement deposition surface into a urine collection canal or channel via a gradient or slope of the disposition surface, and the feces is carried off mechanically, in a direction deviating from the gradient direction, and with maintenance of a distance from the urine collection channel, whereby the deposition surface gradient is maximally of a magnitude such that after deposition the feces remains lying securely on the deposition surface.
In addition, during the pressing the dried feces is preferably pressed into pressed pieces having a size corresponding to their intended use, preferably into pellets or briquettes. In this form, the dried feces can be packed for example into bags or other transport receptacles, and can be easily transported. Because the volume of the dried feces is very small in comparison to previously occurring quantities of liquid manure, the dried feces can also be economically stored and transported over large distances, so that it can also be taken to more remote areas at a reasonable expense.
As an additional measure against a formation of germs in the feces, or in order to exterminate germs that may be found in the feces as a result of animal diseases, the feces can be impregnated or coatedxe2x80x94before the drying or before or after the pressingxe2x80x94with a dry, powdered disinfecting agent. For example, calcium hydroxide or calcium oxide can be used as a disinfecting agent.
The pressed fecal pieces can advantageously be used as dung, for example for field surfaces or grassland, or for horticulture or vegetable gardening. Since no decomposition takes place in the dried feces, a longer storage time no longer presents a problem: all nutrients in the dried feces remain fully maintained. It is also advantageous that the dried feces comprises a neutral pH value of about 7, so that its application does not contribute to the acidification of the soil. Alternatively, it is also possible to use the pressed fecal pieces as fuel. The pressed fecal pieces reach a calorific value of more than 5000 kcal, corresponding approximately to the value of dried oak wood. Because the content of harmful materials, in particular the heavy metal content, of the pressed fecal pieces is very low, a correspondingly clean burning, with exhaust gases low in harmful materials, can be achieved. Only carbon dioxide and water occur as the main combustion products.
With respect to the urine that occurs, it is preferably provided that after its drainage from the stall this urine be used, in untreated form or after a further treatment, for irrigation with a slight dunging effect. Due to the relatively low content of nutrients and salts in the urine, there is no danger that the application of the urine will result in overdunging or in damage to surface bodies of water and groundwater. The urine can thus partially replace fresh water that is used for irrigation and is correspondingly expensive.
With respect to the further treatment of the urine, it is preferably provided that this treatment takes place through oxidation and/or disinfection. The oxidation achieves in particular a breakdown of organic components still contained in the urine, made up of small portions of feces that can still enter the urine despite the separation. The disinfection has the result that a decomposition, with formation of ammonia or other decomposition materials that are harmful to the environment and are foul-smelling, no longer takes place.
Alternatively, or in addition, the further treatment of the urine can take place by a one-stage or multistage mechanical or mechanical-biological clarification. In such a to clarification, there usefully first takes place a precipitation of solid materials, whereby the urine is freed of nutrients for microorganisms. In the simplest case, this can be achieved already by a two-chamber or three-chamber system.
In addition, the further treatment of the urine can take place through vaporization of its liquid portion and, if necessary, drying of the remaining solid substances. In this way, on the one hand there arises essentially water vapor, which can be released into the air without the risk of environmental damages, and on the other hand there arises a remaining solid substance, which can either be reused as xe2x80x9csludge,xe2x80x9d for example as dung, or which can, as explained above in relation to the feces, likewise be dried and then reused in the same manner as the dried feces.
In order to enable the method to be executed as economically as possible, it is preferably provided that heat energy from stall exhaust air heated by animal body heat is used for the drying of the feces and/or for the vaporization of the liquid portion of the urine and/or for a pre-heating of fresh air to be supplied to the stall. The animals kept in the stall present a source of heat energy that constantly produces an excess of heat. Previously, in standard stalls, this heat has simply been blown into the environment with the ventilating air, without deriving an advantage from the heat energy. With the present invention, the heat energy of the stall exhaust air is put to rational use, whereby a possible lack of heat energy can be supplied from other energy sources as needed, for example by means of burning of pressed pieces of dried feces, or from conventional liquid, gaseous, or solid fuels, or through electrical energy.
In order to avoid possible odor and dust pollution from exhaust air, it is further proposed that exhaust air occurring during the drying and/or during the vaporization be conducted through at least one filter that reduces or removes odors and/or dust, and released into the atmosphere.
In addition, the invention proposes that at least one partial current of the stall exhaust air be disinfected before or after its use for drying the feces and/or for vaporizing the liquid portion of the urine, and then used immediately for the aeration of the urine, for the oxidation and/or disinfection thereof. The disinfected airstream itself has an effect on the urine aerated therewith that is at least oxidizing, and, to the extent that disinfecting substances are also contained in the airstream, is also disinfecting.
The disinfection preferably takes place by irradiation of the urine and/or of the stall exhaust air with UV radiation or gamma radiation. Besides a disinfection, the cited radiations achieve at the same time a destruction of organic molecules, so that in this way, for example antibiotics can also be destroyed. Given irradiation of the exhaust air with UV radiation, there arises ozone, which has a disinfecting effect, and with which the aeration of the urine and the simultaneous disinfection thereof can for example also take place.
Overall, with the inventive method and its developments an effective reduction of stress on the environment is achieved with respect to soil and water. Since it is no longer necessary to store and apply liquid manure, excess nitrates no longer enter into the soil and into the surface water. The nutrient content of the excrement stands at approximately 85 to 99% in the feces and in the dried feces produced therefrom. In this way, in contrast to the application of liquid feces, a well-directed dunging, in particular a dunging in accordance with needs and time, is possible. With the inventive method, the previous sources of ammonia that are to be rated as harmful, namely stalls, containers of liquid manure, and surfaces for the application of liquid manure, are freed almost entirely of their harmful properties.
For the solution of the second part of the object of the invention, an apparatus for executing the method that is characterized in that via the carrying-off paths urine and feces can be carried out of the stall in a fresh state before the beginning of a decomposition, and can be supplied to the storage or further treatment means, and in that the apparatus for the further treatment of the feces comprises at least the following apparatus parts:
a device for the surface enlargement of the fresh feces, and
a drying device for drying the feces to a moisture content that prevents a decomposition.
With an apparatus constructed in this way, the method according to the invention, explained above, can in principle be carried out, so that the cited advantages are achieved.
In addition, the apparatus for the further treatment of the feces preferably comprises a pressing device for the production of pressed fecal pieces, having a residual moisture content that prevents a decomposition, from feces that has first been dried in the drying device only to a moisture content between approximately 10 and 25 weight percent. The pressing device necessarily provides a reduction of moisture in the feces due to the pressure exerted, so that a less extensive preliminary drying in the drying device is sufficient, which saves drying time and energy.
As a development of the apparatus for the execution of the method presented above, a separating apparatus is provided that offers, with a relatively low technical expense, a reliable and maximally complete separation of the excrement into urine on the one hand and feces on the other hand.
In a further construction, it is preferably provided that the stall is constructed, at least over a part of its floor surface, with a slatted floor, and that the surface for the deposition of the excrement is the bottom surface of a canal or channel arranged underneath the slatted floor, and that the gaps in the slatted floor and the direction of the gradient run essentially parallel to one another. This construction of the apparatus offers in particular the advantage that the mechanical feces removal device does not move in an area occupied by the animals. In this way, the animals are not disturbed or endangered by the removal device. Through the parallel orientation of the gaps in the slatted floor and the direction of the gradient, it is in particular achieved that the feces deposited on the deposition surface cannot form a xe2x80x9cdamxe2x80x9d that could prevent the urine from flowing into the urine collection canal. Rather, here it is achieved that the urine flows into the urine collection canal between the feces deposited in the direction of the gaps, without hindrance and without carrying feces along with it.
Various technical solutions are possible for the feces removal device. A first solution provides that the feces removal device is formed by a feces blade that can preferably be moved parallel to the urine collection conduit.
An alternative construction of the feces removal device provides that the deposition surface is constructed as a conveyor that can be moved preferably parallel or transverse to the urine collection canal, in the form of one or more flexible conveyor belts or articulated slat conveyors. The conveyor belt or slat conveyor can be constructed with a closed or perforated surface; if perforations are present, the urine can flow off through these while the feces remains on the surface, so that in this construction the gradient of the deposition surface can be omitted.
All the constructions of the feces removal device achieve on the one hand a hindrance-free carrying off of the urine into the urine collection canal, and on the other hand a removal, separate therefrom, of the feces, with the maintenance of a distance from the urine collection canal. In practice, it is sufficient to set into operation the feces removal device at an interval of a few hours, for example approximately three hours, in order to remove the feces that has occurred in the meantime. In such a time period, the feces remain fresh, i.e., no significant decomposition processes have yet begun therein.
Additional preferred and advantageous constructions and developments of the apparatus for the execution of the method are provided, whereby these constructions of the apparatus ensure in particular the execution of the method constructions further explained above, with suitable technical means.